Method for manufacturing a suprastructure and a corresponding drill jig

ABSTRACT

The invention concerns a method for manufacturing a suprastructure ( 7 ) with artificial teeth ( 8 ) which is mounted on at least one implant ( 9,10 ) that is provided in the cavity of the mouth of a person and that has to be fixed to the bone of the lower jaw or the upper jaw ( 1 ), whereby a drill jig ( 3 ) is manufactured with at least one opening ( 4 ) for performing a boring ( 5 ) in the bone for mounting said implant ( 9,10 ), with the feature that the position of said opening ( 4 ) in the drill jig ( 3 ) and the position of the latter is determined in relation to at least one reference organ ( 2 ) that is fixed to said bone.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates to a method for producing a superstructureprovided with artificial teeth, which superstructure is fitted on atleast one implant, which is provided in the oral cavity of a person andhas to be fixed in the bone of a lower or an upper jaw, an aligningplate with at least one aperture being produced for the purpose ofdrilling a hole in the bone through said aperture, in order to fit theabovementioned implant.

2. Prior Art

The method used according to the prior art for producing such asuperstructure is very laborious and protracted for a patient. In afirst step, a wax model of a dental prosthesis is made using animpression that is taken of the patient's jaw. A replica of this waxmodel is then prepared in synthetic resin, in which replica openings arealready provided, corresponding to a possible position for the implants,for the purpose of drilling holes in the jaw. A so-called CT scan thenhas to be made of this replica when it has been placed on thecorresponding jaw of the patient, in order to determine the anatomicalbone structure and the precise location of nerve bundles and bloodvessels. In this way it is checked whether the drilling of holes for theimplants is possible, taking into account the anatomical structure ofthe jaw, such as, inter alia, the position of nerve bundles or bloodvessels present there. If it is found that the proposed position of theimplants is unsuitable because, for example, nerve bundles or bloodvessels would be touched during the drilling of holes, a new or anadapted model has to be produced.

In a subsequent step, an aligning plate is then produced on the basis ofthe abovementioned replica, and the implants are placed in position.When these implants have been placed and the gums and the bone havehealed after this surgical procedure, a number of impressions of the jawtogether with the implants are taken, in order to produce a provisionalmodel, i.e. a wax model, of the superstructure. This provisional modelthen has to be fitted on the patient If the provisional model issatisfactory, the final superstructure is produced on the basis of thisprovisional model.

In a variant of the above method, the abovementioned first step is tomake a CT scan of the jaw on which the superstructure is to be fixed,and an aligning plate is produced directly, on the basis of theelectronic information from this CT scan. The superstructure is thenfurther produced according to the technique described above.

Owing to the different steps required in the case of these processes, apatient generally undergoes six months of treatment before a finalsuperstructure is fitted.

Another method according to the prior art makes use of prefabricatedsuperstructures. However, a disadvantage of this method is that forfitting of the superstructure part of the bone of the upper jaw or ofthe lower jaw has to be removed Furthermore, the prostheses placed inthis way are not adapted to the individual shape of a person's jaw.

OBJECT AND SUMMARY OF THE INVENTION

The object of the invention is to overcome the abovementioneddisadvantages by proposing a method that allows holes that are necessaryfor the placing of implants to be drilled in a very simple and accuratemanner. This method has the further advantage that the production of asuperstructure and its fitting on a person's jaw can be performed in avery short time.

To this end, at least one reference element is fixed to theabovementioned bone, and the location of anatomical structures of theabovementioned jaw relative to this reference element is thendetermined, means being provided on the abovementioned aligning platefor fixing the latter on the abovementioned jaw relative to theabovementioned reference element and, taking into account the determinedlocation of the anatomical structures, the position of theabovementioned aperture in the aligning plate is determined in such away that critical anatomical structures, such as nerve bundles or bloodvessels, are not touched during the drilling of the abovementioned holewhen the aligning plate has been fixed on the abovementioned jaw.

A screw is expediently fixed in the abovementioned bone, said screwforming the abovementioned reference element According to a specialembodiment of the method according to the invention, means are providedon the abovementioned aligning plate for fixing the latter detachably onthe abovementioned reference element before the abovementioned hole isdrilled in the bone. More particularly, the abovementioned means areformed by providing an opening in the aligning plate, which openingconnects up in a virtually exact fit with the abovementioned referenceelement.

According to a preferred embodiment of the method according to theinvention, a dental impression is made of the abovementioned jaw withthe abovementioned reference element, and a provisional model of theabovementioned superstructure with teeth is made on the basis of thisimpression, a three-dimensional image being made of the abovementionedjaw together with this provisional model and the abovementionedreference element

In an advantageous manner, the abovementioned aligning plate is made onthe basis of the abovementioned three-dimensional image.

The abovementioned three-dimensional image is preferably processedelectronically in order to produce the abovementioned aligning plateand/or the abovementioned superstructure by means of a so-called rapidprototyping technique.

According to an advantageous embodiment of the method according to theinvention, the abovementioned aligning plate is fixed to theabovementioned reference element, and the abovementioned hole is drilledin the jaw, and the implant is fixed in said hole, and subsequently,preferably after the abovementioned reference element has been removed,the abovementioned superstructure is fitted on said implant.

The invention also relates to an aligning plate for use of the method,having at least one aperture for drilling a hole in the bone of a loweror an upper jaw of a person, in order to place at least one implant.Said aligning plate is characterized in that it has means for fixing itto at least one reference element that is provided in the abovementionedbone.

Said means preferably have an opening that connects up in a virtuallyexact fit with the abovementioned reference element, so that thealigning plate can be fixed detachably on the reference element by meansof at least one screw or bolt.

BRIEF DESCRIPTION OF THE DRAWING

Other details and advantages of the invention will emerge from thedescription that follows of a number of embodiments of the method andthe aligning plate according to the invention; this description is givenmerely as an example and does not limit the scope of the protectionclaimed; the reference numerals used below relate to the appendedfigures.

FIG. 1 is a diagrammatic top view of a part of a lower jaw withreference elements according to the invention.

FIG. 2 is a diagrammatic top view of a part of a lower jaw with analigning plate according to the invention.

FIG. 3 is a diagrammatic front view of the lower jaw and the aligningplate of FIG. 2.

FIG. 4 is a diagrammatic front view of a part of a lower jaw with asuperstructure provided with teeth according to the invention.

FIG. 5 is a diagrammatic cross section of a reference element togetherwith an aligning plate, according to the invention.

In the various figures the same reference numerals relate to the same orsimilar elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (S) OF THE INVENTION

The invention relates in general to a method for producing a dentalprosthesis which has to be fixed upon so-called, implants provided inthe jawbone of a patient. Such a dental prosthesis comprises a so-calledsuperstructure, on which artificial teeth are provided, in a manner thatis known per se, and which has fixing means for fixing to theabovementioned implants. Apart from that, the invention also relates toa method for producing an aligning plate that makes it possible in asimple manner to drill very accurate holes, in which said implants areplaced.

In the case of the method according to the invention, reference elementsare fixed in the jaw on which the superstructure is to be placed. FIG. 1shows diagrammatically a toothless lower jaw 1 in the case of whichthree reference elements have been fixed in the bone of said jaw. Eachof these reference elements is formed by a screw 2.

Said screws 2 are fixed in different positions in the bone of the jaw 1,in such a way that they project slightly above the gum surrounding thebone. Furthermore, the screws 2 are relatively short; but they are stillsufficiently long, for example almost 5 mm, to be anchored stably in thejaw.

A dental impression of said jaw 1, together with the screws 2, is thenmade in the known manner. On the basis of this impression, a so-calledbite plate is produced, which allows the position of the upper jaw ofthe patient to be determined relative to that of the lower jaw.

Owing to the fact that when the abovementioned impression is beingtaken, the abovementioned screws 2 extend above the gums, during theproduction of the bite plate corresponding hollows are formed in theunderside of the bite plate, which hollows permit said bite plate to bepositioned in an exact position in the oral cavity, the abovementionedhollows connecting up in a virtually exact fit with the screws 2.

By means of this bite plate and a so-called articulator, a wax model isthen prepared, this forming a provisional model for the abovementionedsuperstructure. This wax model comprises a relatively rigid bearingstructure on which artificial teeth are fixed with wax. This provisionalmodel likewise has hollows that correspond to the position of theabovementioned screws 2, in such a way that it can be positionedvirtually perfectly in the oral cavity of the patient.

In a variant of the method according to the invention, theabovementioned hollows are not provided in this provisional model, butsaid hollows are formed during the fitting of the model, throughdepressions being formed in its bearing structure by the abovementionedscrews 2.

After the provisional model has been placed on the corresponding jaw 1of the patient in this way, a three-dimensional image is made of saidjaw 1, together with this model and the abovementioned screws 2.

In order to obtain such a three-dimensional image, it is preferable toperform a so-called CT scan. The information from this three-dimensionalimage is preferably processed electronically, in order to make itpossible to display it in a simple manner on, for example, a computerscreen and to enable it to be used for certain so-called rapidprototyping techniques.

From this three-dimensional image, anatomical structures such as theshape of the bone and the position of the nerve bundles and the bloodvessels in the jaw 1 are deduced. It is then determined at whatpositions in the lower jaw and according to what orientations implantscan be placed in the jaw 1 without touching nerve bundles, blood vesselsor other critical anatomical structures.

On the basis of this information, an aligning plate 3 is produced,having apertures 4 with a suitable orientation and diameter to allowsaid holes to be drilled through them in the bone of the jaw 1, in orderto fit the abovementioned implants. For this purpose, the aligning plate3 is placed on the jaw 1 in the manner shown in FIGS. 2 and 3. Inaddition to these apertures 4, means are also provided for fixing the.aligning plate 3 on the abovementioned screws 2. Said means morespecifically comprise openings, the position of which corresponds tothat of the screws 2, and which can connect up in a virtually exact fitwith the latter.

In this way, the position of the abovementioned apertures 4 isdetermined relative to said screws 2, and the aligning plate 3 assumes afixed position relative to the jaw 1 and the screws 2. This makes itpossible in a simple manner to make a hole 5 by means of a drill, in amanner known per se, for each implant that is to be placed.

For making the abovementioned holes 5 it is preferable to use severalbushes with an axial cylindrical opening, in the case of which theirexternal dimensions virtually correspond to those of the apertures 4, insuch a way that said bushes can be placed in the latter in a virtuallyexact fit with them. The axial cylindrical opening of the various bushesis, however, different. When the holes 5 are being drilled in the jaw 1,more specifically, different drills with increasing diameters are usedin succession. This means that at the start of drilling of a hole 5 adrill with a small diameter is used, in which case a first bush, with acylindrical opening whose diameter corresponds to that of the drill, isplaced in the abovementioned aperture 4 of the aligning plate 3, inorder to guide the drill, so that a very accurate hole can be drilled. Anumber of successive holes are drilled in this way, in each case a drillwith a larger diameter being used, and in each case a bush withcorresponding dimensions being placed in the aperture 4, until the holeobtained in this way is large enough for the placing of an implant

As stated above, the position and the orientation of the abovementionedapertures 4 are selected in such a way that the blood vessels or thenerve bundles 6 or other critical anatomical structures cannot betouched during drilling in the jaw 1.

According to an advantageous embodiment of the method according to theinvention, the aligning plate is made by means of the abovementionedrapid prototyping techniques. Such techniques are, for example,stereolithography, selective laser sintering, fused depositionmodelling, laminated object prototyping, three-dimensional printing, andso forth. In a very interesting rapid prototyping technique theabovementioned aligning plate 3 is produced on the basis of theinformation from the abovementioned three-dimensional image by millingfrom, for example, a block of metal or plastic.

In addition to the abovementioned aligning plate 3, the superstructureis also made using one of these rapid prototyping techniques, starting,on the one hand, from the abovementioned provisional model and theabovementioned hollows that correspond to the position of theabovementioned screws 2, and, on the other hand, from the relativeposition of the abovementioned apertures 4 in the aligning plate 3, ortherefore the desired position of the implants relative to the screws 2.

Through the use of the abovementioned screws 2 as reference elements, itis consequently no longer necessary to make an impression of the jaw 1of a patient after the placing of the implants, and the superstructurecan be produced immediately on the basis of the information from theabovementioned three-dimensional image.

The superstructure is preferably produced by means of a similar rapidprototyping technique to that used for making up the aligning plate 3.

In order to fix the abovementioned artificial teeth in a correctposition on the superstructure 7, the abovementioned provisional modelis placed on a holder, with the abovementioned hollows connecting up ina virtually exact fit with supporting points provided on said holder.The mutual position of said supporting points therefore corresponds tothe mutual position of the abovementioned reference elements. Theprovisional model with the artificial teeth is then cast in a plastic,in order to form a so-called plastic key, said plastic key forming acontact face with the holder. The wax and the bearing structure are thenremoved from the plastic key according to techniques that are known perse, the artificial teeth remaining behind in a fixed position in theplastic. If a setting silicone is used for the abovementioned plastic,said plastic key is called a silicone key.

Finally, in order to fix the artificial teeth on the superstructure, thelatter is placed on the holder, in which case the hollows correspondingto the reference elements connect up in a virtually exact fit with theabovementioned supporting points. In this way the superstructure assumesthe same position relative to the holder as the provisional model duringthe making up of the plastic key. The plastic key is then placed overthe superstructure, care being taken to ensure that the plastic key ispositioned in an identical manner relative to the holder. This iscarried out more specifically by placing the plastic key with the samecontact surface and in the same way against the holder as was the caseduring its manufacture. Finally, a synthetic resin is placed in theplastic key, in a manner known per se, between the superstructure 7 andthe artificial teeth. When this synthetic resin has set, in such a waythat the teeth are immovably connected to the superstructure, theplastic key is removed from the superstructure and the artificial teeth.

FIG. 4 shows diagrammatically a superstructure 7 produced in this way,with artificial teeth 8 placed on it. Said superstructure 7 is fitted onimplants 9 and 10, which are provided in the holes 5 drilled in thelower jaw 1.

FIG. 5 shows diagrammatically a reference element that is formed by ascrew 2. Said screw 2 is fixed through the gum 11 in the bone of a jaw 1and has a preferably polygonal head 12, which extends above the gum 11.The head 12 has on its top side a cylindrical threaded opening 13 whichis coaxial with the screw 2. Fixed in this opening 13 is a bolt 14,which allows the abovementioned aligning plate 3 to be fixed to thescrew 2.

For this purpose, the aligning plate 3 has at a position correspondingto that of the screw 2 an opening that connects up in a virtually exactfit with the head 12 of the screw 2, said opening having a collar 15that rests on the top of the head 12. The abovementioned bolt 14 extendsthrough the opening in the aligning plate 3.

In a variant of the above embodiment of the method and the aligningplate according to the invention, the abovementioned aligning plate 3 isformed by the superstructure 7, so that it is not necessary tomanufactured a separate aligning plate 3. In such a case theabovementioned apertures 4 are made in the superstructure 7, and afterthe implants 9 and 10 have been placed the superstructure is fixed onsaid implants by means of screws or bolts suitable for the purpose.

The reference elements 2 are preferably removed from the jaw 1 beforethe final placing of the superstructure 7.

When reference is made in this description to the bone of a lower or anupper jaw (1), this also includes the bone parts connected to said jaw(1).

Notwithstanding the fact that in the above description and in theappended figures a superstructure that is fixed to a lower jaw with theaid of two implants has been described, the invention also relates to amethod and an aligning plate in the case of which three or more implantsare provided in the lower jaw, or in the case of which only one implantis used. In addition, the dental prosthesis produced in this way neednot extend over the entire jaw 1, but it may have only a few teeth andbe fitted on one implant. The invention is also equally usable forproducing and fitting a superstructure for an upper jaw.

The invention is in no way limited to the embodiments of the method, thesuperstructure and the aligning plate according to the inventiondescribed above and proposed in the figures, but a number of variantscan be considered within the scope of this invention, both as regardsthe reference elements and as regards the dimensions and shapes of thealigning plate.

1. Method for producing a superstructure (7) provided with artificialteeth (8), which superstructure is fitted on at least one implant(9,10), which implant is provided in the oral cavity of a person and isadapted to be fixed in the bone of a lower or an upper jaw (1), and forproducing an aligning plate (3) with at least one aperture (4) servingas a guide for drilling a hole (5) in the bone through the aperture (4)in the aligning plate, in which hole (5) said implant (9,10) is fixed,comprising the steps of: fixing at least one reference element (2) inthe bone, locating anatomical structures of the jaw (1) relative to saidreference element (2), providing fixing means on said aligning plate (3)to fix the aligning plate (2) relative to said reference element (2),having fixed the reference element in the bone and located theanatomical structures relative to said reference element (2), selectinga position for the aperture (4) in the aligning plate (3) relative tosaid fixing means by taking into account the location of the anatomicalstructures so that critical anatomical structures, including nervebundles, are not touched during the drilling of the hole (5) when thealigning plate (3) is fixed to the reference element (2) provided insaid jaw (1) and providing said aperture (4) in the aligning plate (3)according to the selected position for the aperture (4).
 2. The methodaccording to claim 1, wherein a screw (2) is fixed in the bone to serveas the reference element.
 3. The method according to claim 1, furtherproviding means on the aligning plate (3) to detachably fix the aligningplate (3) on the reference element (2) before the hole (5) is drilled inthe bone.
 4. The method according to claim 3, wherein the means areformed by providing an opening in the aligning plate (3), which canconnect up in a substantially exact fit with the reference element (2).5. The method according to claim 1, further making an impression of theabovementioned jaw (1) with the reference element (2), and a provisionalmodel of the superstructure (7) based on said impression, and thereaftermaking a three-dimensional image of the jaw (1) together with theprovisional model and the reference element (2).
 6. The method accordingto claim 5, wherein the three-dimensional image is obtained by carryingout a CT scan.
 7. The method according to claim 5, wherein the aligningplate (3) is produced based on the three-dimensional image.
 8. Themethod according to claim 5, wherein the three-dimensional image isprocessed electronically to produce the aligning plate (3) and/or thesuperstructure (7) by means of a rapid prototyping technique.
 9. Themethod according to claim 1, wherein the aligning plate (3) is fixed tothe reference element (2), the hole (5) is drilled, and the implant(9,10) is fixed in said hole (5), and then after the reference element(2) has been removed, the superstructure (7) is fitted on said implant(9,10).
 10. The method according to claim 1, wherein a three-dimensionalimage is made of said jaw (1) together with said reference element (2),whereby said aligning plate (3) is produced based on thethree-dimensional image by a rapid prototyping technique.
 11. Method forproducing an aligning plate (3) with at least one aperture (4) servingas a guide for drilling a hole (5) in the bone of a lower or an upperjaw (1) through said aperture (4) for fixing an implant (9,10) in thebone, comprising the steps of: fixing at least one reference element (2)in the bone, locating anatomical structures of the jaw (1) relative tosaid reference element (2), providing fixing means on said aligningplate (3) to fix the aligning plate (2) relative to said referenceelement (2), having fixed the reference element in the bone and locatedthe anatomical structures relative to said reference element (2),selecting a position for the aperture (4) in the aligning plate (3)relative to said fixing means by taking into account the location of theanatomical structures so that critical anatomical structures, includingnerve bundles, are not touched during the drilling of the hole (5) whenthe aligning plate (3) is fixed to the reference element (2) provided inthe jaw (1) and providing said aperture (4) in the aligning plate (3)according to the selected position for the aperture (4).
 12. The methodaccording to claim 11, wherein a screw (2) is fixed in the bone to serveas the reference element.
 13. The method according to claim 11, whereinthe fixing means are formed by providing an opening in the aligningplate (3), which can connect up in a substantially exact fit with thereference element (2).
 14. The method according to claim 11, furthermaking an impression of the abovementioned jaw (1) with the referenceelement (2), and a provisional model of a superstructure (7) based onsaid impression, and thereafter making a three-dimensional image of thejaw (1) together with the provisional model and the reference element(2).
 15. Method according to claim 14, wherein the three-dimensionalimage is processed electronically to produce the aligning plate (3)and/or the superstructure (7) by means of a rapid prototyping technique.16. The method according to claim 11, wherein the aligning plate (3) isfixed to the reference element (2), the hole (5) is drilled, and theimplant (9,10) is fixed in said hole (5), and then after the referenceelement (2) has been removed, a superstructure (7) is fitted on saidimplant (9,10).
 17. Method for fixing at least one implant into the boneof a lower or an upper jaw by means of an aligning plate (3) having atleast one aperture (4) serving as a guide for drilling a hole (5) in thebone through said aperture, in which said implant (9,10) is fixed,comprising the steps of: fixing at least one reference element (2) inthe bone, locating anatomical structures of the jaw (1) relative to saidreference element (2), providing fixing means on said aligning plate (3)to fix the aligning plate (2) relative to said reference element (2),having fixed the reference element in the bone and located theanatomical structures relative to said reference element (2), selectinga position for the aperture (4) in the aligning plate (3) relative tosaid fixing means by taking into account the location of the anatomicalstructures so that critical anatomical structures, including nervebundles, are not touched during the drilling of the hole (5) when thealigning plate (3) is fixed to the reference element (2) provided in thejaw (1), providing said aperture (4) in the aligning plate (3) accordingto the selected position for the aperture (4), fixing said aligningplate (3) to the reference element (2) by means of said fixing meansand, successively, guiding a drill through said aperture and drilling ahole (5) in the bone of the jaw (1), fixing said implant into said hole(5).